1 pkg. yellow cake mix
1/2 c. soft butter
1/4 c. firmly packed brown sugar
1/2 tsp. cinnamon
2 apples, thinly sliced
1 c. sour cream
1 egg

Preheat oven to 350 degrees. Combine first 2 ingredients; mix until crumbly. Reserve 2/3 cup for topping; add brown sugar and cinnamon to reserved topping mix. Mix well; set aside. Press remaining mixture onto bottom of ungreased 13 x 9 inch pan. Arrange apple slices over base. Blend sour cream and egg; spread evenly over apple. Sprinkle reserved topping mixture over all. Bake at 350 degrees for 25-30 minutes or until topping is golden brown and bubbly. Serve warm, refrigerate leftovers.